Method of aseptically connecting a fitting to an aseptic storage tank

ABSTRACT

A method of connecting an aseptic fitting to an opening in the top of an aseptic bulk storage tank, whereby asepsis of the tank interior is maintained. The method includes the step of filling the tank interior with liquid chemical sterilant sufficiently to overflow sterilant from the tank into a liquid-retaining enclosure which surrounds the opening in the tank top. This is effective to both sterilize the interior of the tank, and provide a liquid sterilant bath in contact with the openings. The method further includes immersing the fitting in the sterilant bath to sterilize it, and while immersed and in a sterile condition, connecting it to the tank opening, thereby isolating the sterile tank interior from the environment with a sterile fitting. If the fitting includes an internal cavity, sterilization of the fitting prior to its immersion in the bath and connection to the tank can be done by capping the fitting to seal the cavity and autoclaving it. The capped fitting which has been sterilized remote from the sterilant bath is then immersed in the sterilant bath and while immersed connected to the tank opening, to thereby establish communication between the cavity of the fitting and the tank interior while both the cavity and the interior are maintained in a sterile condition.

United States Patent [1 1 Rechtsteiner et a1.

1 Mar. 18, 1975 1 1 METHOD OF ASEPTICALLY CONNECTING A FITTING TO AN ASEPTIC STORAGE TANK [75] Inventors: Steve A. Rechtsteiner; Philip E.

Nelson, both of Cincinnati, Ohio; John R. Heron, West Lafayette, Ind.

[73] Assignee: Purdue Research Foundation, West Lafayette, 1nd.

221 Filed: June 19, 1974 211 Appl. No.: 480,842

Primary E.raminerBarry S. Richman Attorney, Agent, or FirmWood, Herron & Evans [57] ABSTRACT A method of connecting an aseptic fitting to an opening in the top of an aseptic bulk storage tank, whereby asepsis of the tank interior is maintained. The method includes the step of filling the tank interior with liquid chemical sterilant sufficiently to overflow sterilant from the tank into a liquid-retaining enclosure which surrounds the opening in the tank top. This is effective to both sterilize the interior of the tank, and provide a liquid sterilant bath in contact with the openings. The method further includes immersing-the fitting in the sterilant bath to sterilize it, and while immersed and in a sterile condition, connecting it to the tank opening,

' thereby isolating the sterile. tank interior from the environment witha sterile fitting. 1f the fitting includes an internal cavity, sterilization of the fitting prior to its immersion in the bath and connection to the tank can be done by capping the fitting to seal the cavity and autoclaving it. The capped fitting which has been sterilized remote from the sterilant bath is then immersed in the sterilant bath and while immersed connected to the tank opening, to thereby establish communication between the cavity of the fitting and the tank interior while both the cavity and the interior are maintained in a sterile condition,

9 Claims, 5 Drawing Figures PATENTEU W1 81975 SHEET 1. [IF 2 3 M l r 3 \n 1 2 km PATENTED HAR] 81975 SHEET 2 [IF 2 METHOD OF ASEPTICALLY CONNECTING A FITTING TO AN ASEPTIC STORAGE TANK This invention relates to a method of sterilizing a tank and associated fixtures connected to it preparatory to storing bulk materials therein, and more particularly to a method of sterilizing a tank and associated fixtures and aseptically connecting the fixtures to the tank while maintaining asepsis of both the tank and fixtures subsequent to their interconnection.

In the processing of edible material, and prior to final packaging in smaller units for consumer use, it is often necessary to store large quantities of a material in bulk form and to do so under aseptic conditions to insure ultimate purity of the material as supplied to the consumer. Often the edible bulk material must remain in the storage tank for protracted periods of time. Such is the case with, for example, tomato products, fruit and the like which are sold throughout the year, yet available for harvesting during only a few months.

In view of the protracted nature of the storage, it is important that all possible steps be taken to avoid admission into the tank of contaminants, such as microorganismw which when admitted in only small quantities will eventually contaminate the entire tank. To this end the practice has developed of substituting, with microbiologically filtered oxygen-free inert gas, oxygencontaining air which collects in partially filled tanks in the unused volume above the bulk material. By removing oxygen from the unused portion of the tank above the bulk material, multiplication of contaminants, such as micro-organisms, within the tank is inhibited.

Typically, substitution of oxygen-containing air within the unused portion of the tank is accomplished by connecting a pressurized source of nitrogen to theinterior of the tank at or near its top, i.e., above the maximum bulk material level to which the tank is filled. Since it is not practical to provide an aseptic source of pressurized nitrogen, it is necessary to provide filtering means, typically incorporating a nitrogen-pervious micro-biological filtering element, between the nonaseptic nitrogen source and the aseptic storage tank. The nitrogen-pervious filter element incorporated within the filter assembly has a predetermined filtering capacity which, once depleted through use, renders it no longer satisfactory as a filter element. It therefore becomes necessary to periodically replace the filter element. Such replacement typically is accomplished when the tank is empty by disconnecting the filter assembly from the tank, replacing the spent filter element with a fresh one, and thereafter reconnecting the filter assembly with its new filter element to the tank. Obviously, the filter assembly must be sterilized when connected to the tank; otherwise it would constitute a potential source of contamination for bulk material subsequently stored in the tank.

It has also been the practice to provide aseptic storage tanks with suitable accessory fittings such as transparent windows with which to view the interior of the tank, rupture elements which will vent the tank in the event it becomes overpressurized thereby preventing rupture of the tank, and the like. Obviously, such fittings must be sterile prior to connection to the tank, and the sterile condition of both the fittings and the tank interior maintained during the Connection process to avoid potential sources of contamination for bulk material subsequently stored in the tank.

when the tank is empty, access to the tank interior by maintenance personnel for routine cleaning, repair, and the like. The manhole or opening, of course, must be sealed with a suitable manhole cover or the like after the tank interior has been accessedby maintenance personnel and the sealing of the mahole with the cover must be accomplished in amanner such that the man hole opening once sealed does not represent a source of contaminating micro-organisms and the like.

Accordingly, it has been an objective of this invention to provide a method of sterilizing fittings associated with an aseptic storage tank and connecting them under aseptic conditions to the tank such that asepsis of the tank interior is maintained subsequent to interconnection of the fittings and tank. This objective has been accomplished in accordance with certain principles of the invention by providing a bath of liquid chemical sterilant in a liquid enclosure which surrounds an opening in the sterile tank to which a fixture is to be connected, thereby effectively bathing the opening in sterilant. An unsterilized fitting, such as a manhole cover, viewing window, filter assembly, rupture disc, or the like, is then immersed in the bath of liquid sterilant wherein it is rendered sterile. While immersed in the sterilant bath and in a sterilized condition, the fitting, e.'g., the viewing window, rupture disc, manhole cover, filter assembly, or the like is connected as desired in alignment with the tank opening, thereby isolating the aseptic interior environment with the sterile fitting under conditions which maintain asepsis of the tank interior.

in a preferred form of the invention the tank interior is sterilized and the tank opening to which the fitting is to be connected bathed in chemical sterilant by filling the tank with liquid chemical sterilant sufficiently to overflow the sterilant into the enclosure surrounding the opening. After the fitting is sterilized by immersion in the overflow sterilant bath and connected to the tank while so immersed, the sterilant bath in the enclosure surrounding the opening to which the fitting is now connected is drained as is the sterilant located within the tank interior. This leaves the sterile tank with its interconnected sterile fitting ready for storage of bulk material such as food and the like.

In accordance with certain additional principles of this invention, particularly useful with fittings having internal cavities therein, such as filter assemblies, sterilization of the fitting and interconnection thereof toan opening in the tank while maintaining the aseptic condition of the tank interior is accomplished by sterilizing the fitting remote from the sterilant-flooded enclosure bathing the tank opening and, while in sterilecondi tion, capping a port in the sterilized fitting which communicates with the cavity thereof. The capped and sterilized fitting is then immersed in the sterilant bath present in the flooded enclosure surrounding the tank opening to which the fitting is to be connected, and while so immersed the cap removed and the uncapped fitting connected to the tank opening. In this way, the sterile interior ofa fitting, such as a filter assembly, establishes communication with the sterile tank interior without destroying asepsis of either the filter or the tank.

In a preferred form of the invention the cavitycontaining fitting, such as a filter assembly, is sterilized remote from the flooded enclosure surrounding the tank opening to which the filter is to be connected by autoclaving the filter assembly which, before the autoclaving operation, is capped to seal the cavity. If desired, the cavity-containing fitting, instead of being sterilized remote from the sterilant-flooded enclosure surrounding the opening in the tank to which the fitting is to be connected, could be sterilized by immersing it in the sterilant-flooded enclosure in an uncapped condition such that the fitting, including its cavity, is sterilized as a consequence of the immersion in the sterilant bath of the flooded enclosure, whereafter the sterile fitting, while still immersed, is connected to the opening in the tank.

These and other advantages and objectives of the invention will become more readily apparent from a detailed description of the invention taken in connection with the drawings in which:

FIG. 1 is a front elevational view, partially exploded, of an aseptic storage tank, showing the associated fittings which, after sterilization, are connected to suitable openings in the aseptic tank in accordance with the method of this invention whereby asepsis of both the fittings and the tank interior are maintained;

FIG. 2 is a plan view of a portion of the top of the tank showing the fittings connected thereof, taken gen erally along line 22 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 3A is a cross-sectional view of the capped end of the filter assembly; and

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 2;

Aseptic bulk storage tanks of the type to which the fitting sterilization and interconnection method of this invention relates, as shown in FIG. 1, typically include, among other things, a large storage tank 10, e.g., 20,000 or more gallon capacity, in which previously sterilized bulk material, such as crushed tomatoes, fruit or the like, is adapted to be stored under aseptic conditions. Preferably the storage tank has a cylindrical midsection 11 closed at the bottom'with a conical, or funnel-shaped, section 12 and at the top with a domed section 13, the latter section being provided with a selectively removable cover 14 which seals a manhole or access opening 15. The access opening or manhole 15 in combination with the selectively removable manhole cover 14 permits maintenance personnel to enter the interior 16 of the tank for maintenance, cleaning, repair and like purposes. The funnel-shaped bottom section 12 facilitates removal of stored material from the tank interior 16 by gravity action.

The tank 10 is also provided with an inlet/outlet pipe 17 at the lowermost portion, or apex, of the funnelshaped section 12. Bulk material passes through the inlet/outlet pipe 17 when the tank is being filled, being emptied, or a sample of stored material removed for testing. Interconnected between the tank inlet/outlet pipe 17 and a main bulk material conveying pipe 18 is an aseptic valve means 19. The valve means 19 facilitates filling and emptying the tank 10 with bulk material, and in conjunction with other suitable aseptic plumbing connected thereto permits removal of samples of stored material from the tank for test purposes. One form of aseptic valve suitable for use in this invention is disclosed in the copending application of Steve A. Rechtsteiner et al, entitled Aspetic Bulk Material Storage System And Improved Aseptic Valve Therefor, Ser. No. 467,460, filed May 6, 1974, the entire disclosure of which is incorporated herein by reference.

Also associated with the aseptic bulk storage tank is a filter assembly 23 connected at its upstream end 24 to a pressurized, unsterilized oxygen-free gas source 24A such as nitrogen. At its downstream end 25,, the filter assembly 23 is connectable to the tank 10 foz communication with the interior 16 thereof via the opening 26 formed in the manhole cover 14 which is surrounded by a flange 27. Located within a cavity 28 in the filter assembly 23 is a tubular gas-pe'rvious microbiological filter element 29 for filtering the unsterilized nitrogen gas input to .the filter assembly 23 at its upstream end 24. The tubular filter element 29 defines an elongated chamber 30 which communicates solely with the downstream end 25 of the filter assembly 23. A preferred nitrogen filter assembly 23 is disclosed and claimed in the copending application of Steve A. Rechtsteiner et al, entitled Aseptic Storage System For Bulk Materials And Improved Microbiological Filter Therefor, Ser. No. 466,672, filed May 3, 1974, the entire disclosure of which is incorporated herein by reference.

The unsterilized nitrogen entering the upstream end 24 of the filter assembly 23, after suitable microbiological filtering by the filter element 29, enters the tank 10 via downstream end 25 and fills with nitrogen the. unused volume of the tank interior 16 above the surface of bulk material stored therein. In this way, air located in the unused volume above the bulk material, which contains oxygen and supports the growth of contaminating micro-organisms, is substituted by nitrogen which does not support micro-organism growth.

The aseptic storage tank 10 is also typically provided with at least one viewing window assembly 31. The viewing window assembly 31 is mounted to the manhole cover 14 in alignment with an opening 32 provided therein. With the viewing window assembly 31 so mounted, the opening 32 is sealed, yet the contents of the tank are visable from the exterior. Preferably two viewing window assemblies 31, 31', identical in structure and aligned with openings 32 and 32 in the manhole cover 14, are associated with tank 10. The viewing panels 31 and 31 may be disposed'on opposite sides of the flanged opening 27 with respect to which the filter assembly 23 is aligned.

The aseptic storage system also typically includes a rupture disc assembly 34. The rupture disc assembly 34 is connectable in use to the manhole cover 14 in alignment with an opening 35 provided in the manhole cover. The rupture disc assembly 34 includes a rupturable disc which when the assembly 34 is mounted in alignment with the opening 35 in manhole cover 14 seals the opening 35. However, should the pressure or vacuum in the tank interior l6 exceed a predetermined rupture limit, the rupture disc is ruptured, venting the interior ofthe tank to atmosphere via a pipe 36 forming part of the rupture assembly. Pipe 36 protects the disc 62 against accidental rupture should an object inadvertently be dropped on the disc. Pipe 36 also protects against dirt or other foreign material from reaching the disc 62.

Surrounding the manhole 15 formed in the top of the domed tank section 13 is a dual purpose enclosure 37, preferably in the form of a hollow cylinder welded to the dome along its bottom circular edge 38. The enclosure 37 defines a liquid-retaining enclosed volume 39 surrounding the manhole opening 15 in the tank and the openings 26, 32, 32' and 35 in the manhole cover. The tubular enclosure 37, in addition to establishing a liquid-retaining volume 39 surrounding the access opening 15 in the tank dome l3 and the openings 26, 32, 32 and 35 in the manhole cover 14, also establishes, when capped with a suitable cover 40, an enclosed chamber which can during winter months be conveniently heated if the temperatures and conditions justify it.

With reference to FIG. 3, the manhole or access opening 15 in the domed top section 13 of the tank is surrounded by a rim 41 having an upper annular surface or seat 42. The seat 42 cooperates with the marginal bottom surface 43 of the manhole cover periphery 44. A suitable annular gasket 45 is located between the cooperating annular confronting surfaces 42 and 43 of the rim 41 and cover periphery 44, respectively, to serve as a seal there-between when the manhole cover 14 is secured to the manhole-surrounding rim 41 with suitable means such as threaded fasteners 46. Fasteners pass through oversized holes formed in the periphery 44 of the manhole cover 14 and threadedly engage suitable threaded blind holes formed in the manholedefining rim 41.

The manhole cover 14, which is preferably circular and sufficiently larger in diameter than the manhole to the threaded fasteners 46, is provided with openings 32, 32, 26 and 35 to which is fastened in alignment therewith viewing window assemblies 31 and 31, filter assembly 23, and rupture disc assembly 34, respectively. Openings 32, 32, 26 and 35 are surrounded by rims 50, 50, flange 27 and rim 51, respectively. The rims 50, 50, 51 and the flange 27 are structurally integral with the manhole cover 14.

The viewing window assembly 31 includes an annular disc 53 having a central aperture 54 therein. Sand-' wiched between the annular disc 53 and the rim 50 is a transparent glass plate or viewing window 55. Annular gaskets 56 and 57 disposed between the apertured disc 53 and the rim 50 on opposite sides of the transparent window 55 seal the plate or window 55 relative to the manhole cover opening 32 when the window is secured in place over the opening, by tightening threaded fasteners 58. Fasteners 58 pass through suitably located holes in the annular disc 53 and threadedly engage threaded blind holes formed in the rim 50.

Since the viewing window assembly 31' is identical in structure to viewing window 31, further description of viewing window 31' is considered unnecessary. Viewing window assembly 31 is shown in elevation in FIG. 3, whereas viewing window assembly 31 is shown in vertical cross-section in FIG. 3.

The rupture disc assembly 34, as seen in FIG. 4, includes upper and lower annular discs 60 and 61 between which is sandwiched a rupturable disc or membrane 62. Positioned below the rupturable membrane 62 and extending inwardly from the lower annular disc 61 are a pair of fixed blades 64 and 65. Blades 64 and 65 rupture the membrane 62 which moves inwardly against the blades when the vacuum within the tank 10 exceeds that allowed by the structural design of the tank 10. Should the pressure within the tank 10 exceed atmospheric pressure by an amount at least equal to the structural design limits of the tank, the rupture disc 62 will rupture outwardly to relieve the superatmospheric pressure within the tank. Suitable threaded fasteners 66 passing through apertures in the annular disc 60 and threaded in threaded blind holes in the lower disc 61 urge the disc 60 and 61 together clampingthe peripheral margin of the rupturable membrane 62 which is sandwiched therebetween.

An aperture disc 67 to which the inner end of the pipe 36 is connected is bolted to the rim 51 by threaded fasteners 69 passing through holes in the disc 67 and threadedly engaging blind holes in the rim 51. Thus, fasteners 69 secure the disc 67 and integral pipe 36 to the rim 51 surrounding the manhole cover opening 35 with the rupture disc 62 and associated upper and lower apertured discs 60 and 61 in alignment with the opening 35. Gaskets 70 and 71 located adjacent the upper and lower discs 60 and 61 are provided to enhance sealing.

As shown in FIG. 3, the downstream end 25 of the filter assembly 23 is in the form of an apertured disc 72 secured to the lower end-of a pipe section 73. The pipe section 73 of the downstream end 25 of the filter assembly 23 is isolated from the upstream end 24 of the filter assembly by the filter element 29 located in the cavity 28 within the filter assembly. In use, the apertured disc 72 extending from the lower end of pipe 73 seats on the upper edge of flange 27 surrounding manhole cover opening 26, whereat it is maintained by a suitable circular clamp 75 which urges the periphery of the disc 72 into contact with the upper edge of the flange. A suitable annular gasket 77 is positioned between the mating surfaces of the flange 27 and the disc 72 to enhance the seal therebetween. When the filter assembly 23 is connected to the flanged opening 26 of the manhole cover 14, the interior 30 of the tubular filter element 29 disposed within the cavity 28 formed in the filter assembly 23 communicates with the interior 16 of the tank 10. i

- Thus, with the manhole cover secured in place to the manhole-defining rim 41 by suitable fasteners 46, andwith openings 32, 32 and 35 sealed by viewing assemblies 31 and 31 and rupture disc assembly 34 via fasteners 69, respectively, and with the flanged opening 26 connected to the downstream end 25 of the filter assembly 23, the interior 16 of the tank 10 is isolated form the environment. Assuming the tank interior 16 and manhole cover 14 and associated assemblies 31, I

31, 34 and 23 are sterile prior to mounting the manhole cover to the rim 41 and the assemblies 31, 31', 23 and 34 to the manhole cover 14, and further assuming that such asepsis is maintained during the interconnection process, the interior of the tank 16 will remain in an aseptic condition subsequent to interconnection and mounting of the various assemblies 31, 31, 23 and 34 and the manhole cover 14.

The interior16 of the tank 10 and the various fittings and the sterilant overflows through the manhole 15 into the enclosed volume 39 established by the liquidretaining tubular enclosure 37 to establish a sterilant bath 78. By means of an overflow pipe 80 communicating with the enclosed volume 39 and a drain connected is bathed in sterilant thereby sterilizing the manhole and the associated seat 42 of manhole-surrounding rim 41.

The manhole cover 14 and gasket 45, not yet sterilized, are preferably totally immersed in the sterilant bath 78 located in enclosed volume 39, thereby sterilizing manhole cover 14 and its associated seat 42 and gasket 45. With manhole cover 14 and associated seat 42 and gasket 45 sterilized, and while still immersed in bath 78, the manhole and gasket are fastened to rim 41 surrounding the manhole 15 in alignment with the manhole by tightening threaded fasteners 46, which fasteners are also sterilized by reason of being immersed in the sterilant bath 78. With the manhole cover 14 secured to the tank and immersed in the sterilant bath 78, manhole openings 32, 32', 26 and 35 are bathed in sterilant, sterilizing these openings.

The viewing window assemblies 31 and 31, yet unsterilized, are also completely immersed in the liquid sterilant bath 78 thereby sterilizing these assemblies. With the viewing window assemblies 31 and 31' sterilized, and while still immersed in the sterilant bath 78, the assemblies 31 and 31' are secured in position in alignment with their respective manhole cover openings 32 and 32' by tightening fasteners 58 and 58'. Thus, openings 32 and 32' in manhole cover 14 are now sealed with respect to the environment by the sterilized assemblies 31 and 31'.

The rupture disc assembly 34, and in particular the elements 61, 62, 64, 65 and the gasket 71 which will communicate with the interior 16 of the tank 10, are immersed in the liquid sterilant bath 78, thereby sterilizing them. With the rupture disc assembly 34 so sterilized, and while still immersed in the liquid sterilant bath 78, the sterile assembly is secured to the manhole cover 14 in alignment with the opening 35 by tightening threaded fastener 69. The opening 35 in the manhole cover 14 is now sealed with respect to the environment by the sterilized rupture disc assembly 34.

The filter assembly 23, in a preferred form of the invention, is provided with a cap 85 secured to downstream end of disc 25 by a suitable circular clamp 75 to seal the pipe 73 which communicates with the interior cavity 30 of the filter element 29 located within filter assembly 23. The yet unsterilized filter assembly 23, which now has its downstream end 25 sealed by cap 85, is placed in an autoclave and thereby sterilized. Since the filter element 29 establishes a micro-organism barrier between the downstream end 25 of the filter assembly 23 which when assembled on the manhole cover 14 communicates with the tank interior 16 and the upstream end 24 which communicates with the source of unsterilized nitrogen gas, it is unnecessary to cap the upstream end of the filter assembly.

With the downstream end 25 of the filter assembly 23 capped and the cavity 30 of filter element 29 which in use communicates with the tank interior 16 sterilized, the capped downstream end of the filter assembly 23 is immersed in the sterilant bath 78. While the capped downstream end 25 of the filter assembly is so immersed, a circular clamp 75, which secures thecap to disc 72, is loosened and the cap 85 removed exposing the sterile filter cavity 30 of the filter assembly 23 to the interior of the tank 10 via manhole cover opening 26. With the uncapped downstream end 25 of the filter assembly still immersed in liquid sterilant bath 78, the disc 72 at the downstream end of the filter assembly is secured to the upper edge of the flange 27 with the gasket 77 sandwiched therebetween by means of the circular clamp 75. The sterile interior cavity 30 of filter element 29 of assembly 23 now communicates with the sterile interior 16 of the tank 10. Stated differently, the interior 16 of the tank 10, and in particular the flanged opening 26 in the manhole cover 14, is isolated from the environment by means of the microbiological filter element 29, the interior 30 of which has been sterilized and remains sterilized throughout the process of interconnecting the filter assembly 23 to the manhole cover 14.

As an alternative to sterilizing filter assembly 23 independent of sterilant bath 78 by autoclaving the filter assembly and capping the downstream end 25 prior to immersion of the downstream end in the sterilant bath 78 for connection to the flanged opening 26, the unsterilized filter assembly 23, with the downstrean end 25 uncapped, could be immersed in the liquid sterilant bath 78 and the filter assembly, including cavity 30 of filter element 29, sterilized thereby. Assuming sterilization was accomplished in bath 78, and while still immersed in the bath 78, the uncapped and now sterile filter assembly 23 could then have its downstream end 25 secured to the flanged opening 26 with clamp 75, in the manner previously described, 'to isolate manhole cover opening 26 from the environment via the sterilized filter element 29.

By virtue of the foregoing described process, not only has the entire interior 16 of the tank 10 been sterilized, but the manhole or access opening 15 and the associated manhole cover 14 have been sterilized, as have the openings 32, 32, 26 and 35 in manhole cover 14, and their associated assemblies 31, 31, 23 and 34, respecitvely. Moreover, the sterilized manhole cover 14 has been secured to seal the manhole '15 and the sterile assemblies 31, 31 23 and 34 have been secured in alignment with the respective openings 32, 32', 26

and 35 in the manhole cover 14 without destroying either the aseptic condition of the tank interior 16 of the asepsis of the manhole cover 14 and associated assemblies 31, 31, 23 and 34.

After the tank interior l6, manhole cover 14, and associated assemblies 31, 31, 23 and 34 have been sterilized and interconnected in the foregoing manner under aseptic conditions whereby the aseptic interior 16 of the tank 10 has been maintained, the liquid sterilant in the tank 10 is drained via the inlet/outlet port 17, valve 19 and main conduit 18, and nitrogen added via filter 23 to the tank volume previously occupied by the sterilant. Substitution of the drained sterilant by nitrogen prevents placement of the tank interior under a vacuum condition. Additionally, the liquid sterilant bath 78 in the enclosed volume 39 defined by the tubular enclosure 37 is drained via a drain pipe 90 which communicates with the bottom of the enclosed volume 39 and connects to the overflow pipe 80 at end 81 via a suitable flow valve 91 connected between the pipe 90 and the downstream end 81 of the overflow pipe 80. The aseptic tank with its associated manhole cover and assemblies 31, 31', 23 and 34 secured thereto is now ready to be filled with sterilized bulk material via the main conduit 18, valve 19, and inlet/outlet pipe 17. As the bulk material is introduced into the interior 16 of the tank the nitrogen in the tank, which has been input thereto from a suitable source 24A connected to upstream filter end 24, via the filter assembly 23, is displaced by thhe incoming food by reverse nitrogen flow back through the filter assembly.

A preferred liquid chemical sterilant useful in the process of this invention is disclosed in US. Pat. No. 3,714,956, Philip E. Nelson, issued Feb. 6, 1973. Of course, other liquid chemical sterilants can also be used.

While the invention has been described in connection with aseptically mounting a manhole cover to a tank and mounting two viewing window assemblies, a rupture disc assembly, and a filter assembly to the manhole cover, the tank interior and fitting sterilization and interconnecting process of this invention can be used to sterilize and aseptically mount fittings of other types to a tank whose interior thereof it is desired to maintain under aseptic conditions for subsequent storage of sterilized bulk material.

What is claimed is:

l. A method of aseptically connecting a fitting to an opening in a bulk storage tank, which opening is surrounded by a liquid-retaining enclosure, whereby the fitting communicates with the tank interior, comprising the steps of:

filling the tank with liquid chemical sterilant to sterilize the tank interior,

filling the liquid-retaining enclosure which surrounds the tank opening, while the tank interior is in a sterile condition, with a liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, and

immersing the fitting in the sterilant bath to sterilize the fitting and while immersed and in a sterile condition connecting the fitting to the tank opening to thereby isolate the sterile tank interior from the environment via the sterile fitting.

2. The method of claim 1 wherein the filling step and tank interior sterilizing step includes the step of filling the tank interior with liquid chemical sterilant sufficiently to overflow sterilant from the tank into the enclosure.

3. A method of aseptically connecting first and second fittings to first and second openings, respectively, in a bulk storage tank, which openings are surrounded by a liquid-retaining enclosure, whereby the tank interior is isolated from the environment via the first opening by the first fitting and whereby a cavity in the second fitting communicates with said tank interior, comprising the steps of:

filling the tank with liquid chemical sterilant to sterilize the tank interior,

filling the enclosure which surrounds the tank openmgs, while the tank interior is m a sterile condition,

with a liquid chemical sterilant to provide a liquid sterilant bath in contact with the openings,

ilize the first fitting and while immersed and in a sterile condition connecting the first'fittingto the first tank opening to thereby isolate the sterile tank interior via said first opening from the environment by the first fitting, sealing and sterilizing the second fitting cavity, and immersing the second fitting in the liquid sterilant bath and while immersed unsealing the sterilized second fitting cavity and connecting the second fitting to the second tank opening whereby communication is established between the second fitting cavity and the tank-interior while both the cavity and interior are maintained in a sterile condition. 4. A method of aseptically connecting a fitting to an opening in a bulk storage tank, which opening is surrounded by a liquid-retaining enclosure, whereby a cavity in the fitting communicates with the interior of the tank, comprising the steps of:

filling the tank with liquid chemical sterilant to sterilize the tank interior, I filling the enclosure which surrounds the tank opening, while the tank interior is in a sterile condition, with a liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, sealing and sterlizing the fitting cavity, and immersing the fitting in the liquid sterilant bath and while immersed unsealing the sterilant bath and while immersed unsealing the sterilized fitting cavity and connecting the fitting to the tank opening whereby communication is established between the fitting cavity and tank interior while both the cavity and interior are maintained in a sterile condition.-

5. The method of claim 4 wherein the step of sealing and sterilizing the cavity of the fitting includes the step of sealing a port in the fitting which connects to the cavity to thereby seal the cavity and sterilizing the cavity remote from the sterilant bath, and wherein the unsealing and connecting step includes, while the fitting is immersed in the sterilant bath, the step of uncapping the port and connecting-the uncapped port to the tank opening.

6. The method of claim 5 wherein the step of sterilizing the fitting cavity includes autoclaving the fitting.

7. A method of aseptically connecting a fitting to an opening in the top of a bulk storage tank, which opening is surrounded by an upstanding liquid-retaining wall, whereby a cavity in the fitting communicates with the interior of the tank, comprising the steps of:

filling the tank'with liquid chemical sterilant to sterilize the tank interior, filling the region defined by the liquid-retaining wall with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening,

sealing and sterilizing the fitting cavity, and

immersing the fitting in the liquid sterilant bath and while immersed unsealing the sterilized fitting cavity and connecting the fitting to the tank opening whereby communication is established between the fitting cavity and the tank interior while both the cavity and interior are maintained in a sterile condition.

8. A method of aseptically connecting a cover to an opening in a bulk storage tank and a fitting to an opening in the cover, which tank opening is surrounded by a liquid-retaining enclosure, whereby the tank interior is isolated from the environment by the cover and fitting, comprising the steps of:

filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the region defined by the liquid-retaining enclosure with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank openmg, immersing the cover in the liquid sterilant bath and while immersed connecting the cover to the tank opening, immersing the fitting in the liquid sterilant bath and while immersed connecting the fitting'to the cover opening, thereby isolating the sterile tank interior from the environment via the cover and fitting while the cover, fitting and tank interior are maintained in a sterile condition. 9. A method of aseptically connecting a cover to an opening in a bulk storage tank and a filter assembly having a cavity therein to an opening in the cover, which tank opening is surrounded by a liquid-retaining enclosure, whereby the tank interior communicates 12 with the environment via the filter assembly, comprising the steps of:

filling the tank with liquid chemical sterilant to sterilize the tank interior, 7 filling the liquid-retaining enclosure surrounding the tank opening with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, sealing and sterilizing the filter cavity remote from the sterilant bath in the enclosure, immersing the cover in the liquid sterilant bath and while immersed connecting the cover to the tank opening, immersing the sealed filter assembly in the liquid sterilant bath and while immersed unsealing the sterilized filter cavity and connecting the filter assembly to the opening in the cover, whereby communication between the filter cavity and the tank interior is established while both the cavity and interior are maintained in a sterile condition. 

1. A METHOD OF ASEPTICALLY CONNECTING A FITTING TO AN OPENING IN A BULK STORAGE TANK, WHICH OPENING IS SURROUNDED BY A LIQUID-RETAINING ENCLOSURE, WHEREBY THE FITTING COMMUNICATES WITH THE TANK INTERIOR, COMPRISING THE STEPS OF: FILLING THE TANK WITH LIQUID CHEMICAL STERILANT TO STERILIZE THE TANK INTERIOR, FILLING THE LIQUID-RETAINING ENCLOSURE WHICH SURROUNDS THE TANK OPENING, WHILE THE TANK INTERIOR IS IN A STERILE CONDITION, WITH A LIQUID CHEMICAL STERILANT TO PROVIDE A LIQUID STERILANT BATH IN CONTACT WITH THE TANK OPENING, AND IMMERSING THE FITTING IN THE STERILANT BATH TO STERILIZE THE FITTING AND WHILE IMMERSED AND IN A STERILE CONDITION CONNECTING THE FITTING TO THE TANK OPENING TO THEREBY ISOLATE THE STERILE TANK INTERIOR FORM THE ENVIRONMENT VIA THE STERILE FITTING.
 2. The method of claim 1 wherein the filling step and tank interior sterilizing step includes the step of filling the tank interior with liquid chemical sterilant sufficiently to overflow sterilant from the tank into the enclosure.
 3. A method of aseptically connecting first and second fittings to first and second openings, respectively, in a bulk storage tank, which openings are surrounded by a liquid-retaining enclosure, whereby the tank interior is isolated from the environment via the first opening by the first fitting and whereby a cavity in the second fitting communicates with said tank interior, comprising the steps of: filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the enclosure which surrounds the tank openings, while the tank interior is in a sterile condition, with a liquid chemical sterilant to provide a liquid sterilant bath in contact with the openings, immersing the first fitting in the sterilant bath to sterilize the first fitting and while immersed and in a sterile condition connecting the first fitting to the first tank opening to thereby isolate the sterile tank interior via said first opening from the environment by the first fitting, sealing and sterilizing the second fitting cavity, and immersing the second fitting in the liquid sterilant bath and while immersed unsealing the sterilized second fitting cavity and connecting the second fitting to the second tank opening whereby communication is established between the second fitting cavity and the tank interior while both the cavity and interior are maintained in a sterile condition.
 4. A method of aseptically connecting a fitting to an opening in a bulk storage tank, which opening is surrounded by a liquid-retaining enclosure, whereby a cavity in the fitting communicates with the interior of the tank, comprising the steps of: filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the enclosure which surrounds the tank opening, while the tank interior is in a sterile condition, with a liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, sealing and sterlizing the fitting cavity, and immersing the fitting in the liquid sterilant bath and while immersed unsealing the sterilant bath and while immersed unsealing the sterilized fitting cavity and connecting the fitting to the tank opening whereby communication is established between the fitting cavity and tank interior while both the cavity and interior are maintained in a sterile condition.
 5. The method of claim 4 wherein the step of sealing and sterilizing the cavity of the fitting includes the step of sealing a port in the fitting which connects to the cavity to thereby seal the cavity and sterilizing the cavity remote from the sterilant bath, and wherein the unsealing and connecting step includes, while the fitting is immersed in the sterilant bath, the step of uncapping the port and connecting the uncapped port to the tank opening.
 6. The method of claim 5 wherein the step of sterilizing the fitting cavity includes autoclaving the fitting.
 7. A method of aseptically connecting a fitting to an opening in the top of a bulk storage tank, which opening is surrounded by an upstanding liquid-retaining wall, whereby a cavity in the fitting communicates with the interior of the tank, comprising the steps of: filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the region defined by The liquid-retaining wall with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, sealing and sterilizing the fitting cavity, and immersing the fitting in the liquid sterilant bath and while immersed unsealing the sterilized fitting cavity and connecting the fitting to the tank opening whereby communication is established between the fitting cavity and the tank interior while both the cavity and interior are maintained in a sterile condition.
 8. A method of aseptically connecting a cover to an opening in a bulk storage tank and a fitting to an opening in the cover, which tank opening is surrounded by a liquid-retaining enclosure, whereby the tank interior is isolated from the environment by the cover and fitting, comprising the steps of: filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the region defined by the liquid-retaining enclosure with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, immersing the cover in the liquid sterilant bath and while immersed connecting the cover to the tank opening, immersing the fitting in the liquid sterilant bath and while immersed connecting the fitting to the cover opening, thereby isolating the sterile tank interior from the environment via the cover and fitting while the cover, fitting and tank interior are maintained in a sterile condition.
 9. A method of aseptically connecting a cover to an opening in a bulk storage tank and a filter assembly having a cavity therein to an opening in the cover, which tank opening is surrounded by a liquid-retaining enclosure, whereby the tank interior communicates with the environment via the filter assembly, comprising the steps of: filling the tank with liquid chemical sterilant to sterilize the tank interior, filling the liquid-retaining enclosure surrounding the tank opening with liquid chemical sterilant to provide a liquid sterilant bath in contact with the tank opening, sealing and sterilizing the filter cavity remote from the sterilant bath in the enclosure, immersing the cover in the liquid sterilant bath and while immersed connecting the cover to the tank opening, immersing the sealed filter assembly in the liquid sterilant bath and while immersed unsealing the sterilized filter cavity and connecting the filter assembly to the opening in the cover, whereby communication between the filter cavity and the tank interior is established while both the cavity and interior are maintained in a sterile condition. 